1. Field of the Invention
This invention relates to the field of data processing systems. More particularly, this invention relates to data processing systems which precharge a node and then discharge that node to represent a data value.
2. Description of the Prior Art
It is know to provide data processing systems which precharge a node and then discharge that node to represent a data value. One example of such a system is a memory in which bit lines running through an array of memory cells are precharged to a precharge voltage. A row of memory cells are then coupled to the bit lines and selectively discharged to the bit lines to represent the data values stored within the memory cells. Another example of a system which precharges a node then discharges that node to represent a data value is one employing domino logic. In domino logic a node is precharged to a precharge voltage then discharged in dependence upon the value of one or more input signals. Further examples of this type of system include signal lines which are used to pass signal values by precharging those signal lines to a precharge voltage and then selectively discharging those signal line to indicate a data value. Such signal lines may, for example, be used to pass signals through silicon vias between die layers of an integrated circuit formed of stacked dies or between integrated circuits using differential input/output signalling on a pair of signal lines.
A problem with such systems is that in order to speed up data processing it is desirable to read the data value from the node as rapidly as possible when the discharge of that node is still taking place, i.e. the node is only partially discharged. Thus, in many cases, such as memory bit lines, it is normal that the voltage of the node is not allowed to discharge completely before the data value is read. While this speeds up operation it introduces a problem of increasing the chances of an incorrect data value being read fro the node, for example, due to noise.
One way of dealing with this difficulty would be to resample the voltage at the node later during the discharge phase to ensure that it agrees with the initially read value. However, such re-sampling may result in the discharge phase having to last longer, thereby slowing operation, and may also require the duplication of some circuit elements needed to perform the sampling.